Animal telemetry is a powerful tool for observing marine animals and the physical environments that they inhabit, from coastal and continental shelf ecosystems to polar seas and open oceans. Satellite-linked biologgers and networks of acoustic receivers allow animals to be reliably monitored over scales of tens of meters to thousands of kilometers, giving insight into their habitat use, home range size, the phenology of migratory patterns and the biotic and abiotic factors that drive their distributions. Furthermore, physical environmental variables can be collected using animals as autonomous sampling platforms, increasing spatial and temporal coverage of global oceanographic observation systems. The use of animal telemetry, therefore, has the capacity to provide measures from a suite of essential ocean variables (EOVs) for improved monitoring of Earth's oceans. Here we outline the design features of animal telemetry systems, describe current applications and their benefits and challenges, and discuss future directions. We describe new analytical techniques that improve our ability to not only quantify animal movements but to also provide a powerful framework for comparative studies across taxa. We discuss the application of animal telemetry and its capacity to collect biotic and abiotic data, how the data collected can be incorporated into ocean observing systems, and the role these data can play in improved ocean management.

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Investigations on the distribution, population size, and habitat characteristics of animal populations provide the baselines for sound conservation management. Southeast Asia is considered an important habitat for the Indo-Pacific humpback dolphin (Sousa chinensis), but information regarding their population size and habitat characteristics is limited. The present study investigated the distribution and habitat characteristics of humpback dolphins off Donsak, Thailand, and estimated the population size based on photo-identification records. Using the POPAN model, the minimum population size of the humpback dolphins off Donsak was estimated to be 193 (167 to 249; 95% confidence interval), with 36 calves, 58 juveniles, 40 subadults, and 59 adults. The progressively ascending cumulative sighting curve implied that the actual humpback dolphin population size in the investigated area is likely higher than this estimate. Principal components analysis of the environmental characteristics indicated that the adult dolphins tend to occur in deeper and clearer waters relative to the younger age classes. Alterations of the coast environment and coastal anthropogenic activities may be particularly deleterious for younger dolphins. Findings from this study contribute significantly to our understanding of the humpback dolphins in Thailand and provide valuable insight for future conservation management.

Optimal feeding frequency was investigated to improve head-started propagation programme of juvenile green turtles (Chelonia mydas). The 15-day-old turtles (25-26 g body weight) were fed for ad libitum intake at one (1MD), two (2MD), three (3MD) or four (4MD) meals daily over a 3-month trial. Responses in growth, feed utilization, faecal characteristics, haematological parameters and carapace elemental composition were used to compare treatment effects. At the end of the feeding trial, no treatment had induced mortality. Growth performance in terms of weight gain and specific growth rate was similar in turtles fed 2MD, 3MD or 4MD (p > 0.05), but 1MD differed from these (p < 0.05), and feeding at excess frequency (3MD and 4MD) increased the within-group size variation. Turtles fed 2MD had significantly lower feed intake than in 3MD and 4MD groups, but the feed conversion ratios were similar. Faecal digestive enzyme analysis indicated higher catabolism of lipid and protein in the deprivation group (1MD), when compared with turtles fed at least twice daily. The feeding frequency did not affect the specific activities of carbohydrate-digesting enzymes. The results on enzymes activities were corroborated by the transition enthalpy characteristics of faeces, indicating nutrients remaining after digestion. The 2MD treatment also improved the haematological characteristics and the carapace quality, relative to low or excess feeding. Overall, the findings indicate that feeding juvenile green turtles twice a day is the preferred option in their head-started propagation. This promotes growth, reduces feed consumption, and improves health and carapace quality.